This is the 35 U.S.C. 371 national stage of international application PCT/IT99/00206 filed on Jul. 6, 1999, which designated the United States of America.
The present invention relates to the mechanical industry and more particularly the machine tools.
It is known that machine tools need cooling liquids to avoid the overheating of the tools during machining. Such cooling liquids (thereafter xe2x80x9ccoolantsxe2x80x9d) are basically water emulsions comprising emulsifying oil and/or other lubricating means.
Machine tools are usually provided with at least a coolant tank and at least a recirculating pump that draws the coolant from the tank for supplying the same to the tool to be cooled.
A common problem in this field is given by the fast deterioration of such cooling emulsions. This is mainly due to the fact that coolant has generally a concentration of emulsifying oil ranging between 3 and 5% and is continuously in contact with the lubricating oil of the guides, the consumption of which in the current machine tools is about one and half litre a day.
Such lubricating oil is not recycled and is collected in the coolant tank with the result that a layer of lubricating oil is formed on the surface of the coolant in a few days, thus preventing the latter from being oxygenated and helping the fast proliferation of anaerobic bacteria that are the main cause of bad smells and fast deterioration of the emulsion itself.
Problems due to the removal of the lubricating oil from the surface of the cooling emulsion in the tank have been not solved effectively until today. An approach uses a suitable electric apparatus so-called oil separator.
A drawback of such oil separator is that not all the oil is recovered but a portion thereof sticks at the metal wall of the tank. If it is true that the service life of the emulsion is prolonged in this way, it is also true that the tank needs a careful maintenance after the replacement of the emulsion to avoid that the mould produced by the bacteria pollutes quickly the new cooling emulsion.
This invention seeks to overcome such drawbacks by providing a device to be installed in the tanks of the cooling liquid in the machine tools capable of preventing anaerobic bacteria from being formed and avoiding both the fast deterioration of the cooling emulsion and bad smell emission.
This is accomplished according to the invention by providing a device able to generate air microbubbles that guarantee the constant, uniform oxygenation of the cooling emulsion, particularly when the machine is still and the coolant is prone to become stagnant.